1. Field of the Invention
The present invention relates to a milking apparatus, i.e. an apparatus for removing milk from a teat of an animal, such as a cow, sheep, goat, horse, buffalo, or camel. It also relates to a method of use of such an apparatus.
2. Summary of the Prior Art
In a conventional milking apparatus, a cylindrical liner of resilient material is housed within an outer body, and the liner is tensioned along the axis of the cylinder. The teat of the animal is then inserted through an opening in the body into the cylindrical liner, and then suction is applied to another opening in the body, at the other end of the cylindrical liner to that in which the teat is inserted, to create a partial vacuum. This partial vacuum draws milk from the teat, but also causes congestion of the teat tissues, arising from the accumulation of blood and other fluids. In order to relieve this congestion, the region between the outer body and the liner is periodically brought to atmospheric pressure. This causes the liner to collapse around the teat, so providing relief from the suction. Such milking apparatuses have been known for around 100 years, and although many modifications to the basic arrangement have been suggested, such as the application of a periodic over pressure around the liner, rather than atmospheric pressure, the basic arrangement has stayed the same. Thus, the basic liner arrangement disclosed in e.g. GB270316, published in 1927, is not dissimilar from e.g. U.S. Pat. No. 6,427,624 published in 2002.
One problem associated with the liner arrangement in the conventional apparatus described above is that, when the region between the body and the liner is brought to atmospheric pressure, the liner closes in tightly around the teat end, so that the end of the teat often experiences excessive local pressure. This means that, in order to avoid damage to the teat end, only low suction forces may be applied to the teat as a whole during milking and any periodic over pressure applied to the outside of the liner must also be kept at a low level. Thus, the efficiency of the milking process is impaired by the need to avoid excessive force being applied to the teat end, so as to maintain teat health.
Recently, improvements have been made to the conventional apparatus described above, so that when the liner closes in around the teat in order to relieve congestion of the teat tissue, it collapses more evenly along the length of the teat. EP1647183 describes a milking apparatus in which the liner has membranes that are held under transverse tension i.e. tension in a direction generally perpendicular to the direction of elongation of the barrel of the teat. The membranes are held under this transverse tension in their normal rest state, i.e. even when the milking apparatus is not in operation and no suction or over pressure is being applied.
The purpose of the transverse tension is to prevent the membranes contracting too closely around the teat end when the milking apparatus is in operation. Thus, excessively high forces and damage to the teat end can be avoided, while at the same time, maintaining the suction forces experienced by the teat at sufficiently high levels to achieve efficient milking action.
The transverse tension in the liners allows the pressure applied to the barrel of the teat to be maintained at useful levels for milking, while at the same time preventing damage to the teat end when the liner collapses around the teat to relieve congestion within the teat. In effect, the transverse tension of the liners allows the liners to collapse more evenly along the length of the teat during milking than is the case in the conventional milking apparatus described above, and so the milking process partly mimics the sucking action of a calf.
In the milking apparatus described in EP1647183, transverse tension of the membranes of the liner is achieved by fixing the membranes to attachment points on the interior walls of the outer body housing the liner or onto rods fixed within the outer body. However, since these attachment points are only accessible from the interior of the body housing the liner, the process of affixing the membranes to the outer body, so that they are under transverse tension, is awkward and time-consuming. Furthermore, the outer body often includes external attachments which make it difficult to manipulate. Another problem is that the attachment of the liner membranes directly to the outer body requires the outer body, which is in general a standard component, to be specially adapted to hold the membranes.